1. Field of the Invention
The present invention relates to a spindle motor.
2. Description of the Related Art
In general, a small spindle motor used in a hard disk drive (HDD) is generally provided with a fluid dynamic bearing assembly, and lubricating fluid such as oil is provided in a bearing clearance formed between a shaft and a sleeve of the fluid dynamic bearing assembly. Fluid dynamic pressure is generated in the oil provided in the bearing clearance while being compressed, thereby rotatably supporting the shaft.
That is, the fluid dynamic bearing assembly generally generates dynamic pressure through thrust dynamic pressure grooves in an axial direction and radial dynamic pressure grooves in a circumferential direction, thereby promoting stability of rotational driving of the spindle motor.
Meanwhile, in accordance with the recent increase in capacity of the hard disk drive, a technical problem in which vibrations generated during driving of the spindle motor should be reduced has arisen. That is, in order to allow the hard disk drive to be driven without an error due to vibrations generated therein during the driving thereof, demand for an improvement in the performance of the fluid dynamic bearing assembly included in the spindle motor has increased.
However, in the case in which the lubricating fluid is pumped by the thrust dynamic pressure groove and the radial dynamic pressure groove as described above, areas of negative pressure (that is, pressure lower than atmospheric pressure) may be generated.
In addition, since rotational characteristics may be deteriorated in the case in which negative pressure is generated, the development of a structure capable of reducing the generation of negative pressure has been required.
In the following Related Art Document, a spindle motor including a thrust plate is disclosed.